Ferrous alloy



1. f h z Gregory J. Comstock, Edgewood, Pa., gnor to Firth-Sterling Steel Company, McKeesport, Pa, a corporation of Pennsylvania No Drawing. Application July 17, 1931 Serial No. 551,547

23 Claims. (01.175- -45) This invention relates generally to ferrous alloys, and more particularly to alloy steels especially adapted for making cutting or forming tools, dies, punches and the like, which combine the desirable properties of exceptional cutting ability, extreme hardness, and great resistance to abrasion.

This application is a continuation-in-part of my copending application Serial No. 310,909, filed October 6, 1928.

Alloy steels are now commonly made by adding I the alloying elements either in the form of ferro-alloys or in elemental form to a steel bath and causing more or less complete dissemination of the alloying elements throughout the bath. When an alloy steel is made in this manner, it is generally possible to predict the approximate physical properties of the steel from its chemical composition.

In the case of the present invention, however, the properties of the alloy are not entirely dependent upon its composition, but, on the contrary, the alloy exhibits certain properties which would not be apparent from its chemical composition, but which depend upon the peculiar method employed in producing the alloy.

In my process of making ferrous alloys, for example alloy steels, an abrasive material is dissolved in a steel bath and a hard constituent containing at least a portion of the components of the abrasive either in their-original or in a modified form is caused to reprecipitate out of solution when the alloy is cast. The abrasives used are compounds of a metal and a metalloid which combine to form a hard abrasive material.

These abrasives impart good cutting properties ,or resistance to abrasion to the alloy. The preferred abrasives are the hard carbides of the metals tungsten, (W3C), (W2C), (WC); chromium, (CrrC), (Cr-1C3), (CraCa); molybdenum, (MoaC), (MoC); vanadium, (V50), (VC); titanium, (TiC); tantalum, (TaC); zirconium, (ZrC); thorium, (ThCz); uranium, (U303); and columbium, (NbC) Within this group of carbides which may be dissolved in a ferrous alloy bath and then reprecipitated to form hard carbides, I prefer to use carbides of metals of the tungsten group,.by which is meant carbides of tungsten, molybdenum, and chromium, particularly tungsten car bide.

In carrying out my process, one or more of the carbides above mentioned or other abrasives are dissolved in a ferrous alloy bath, the amount of carbide or other abrasive and the time of addition to the bath being such that when the alloyis cast a hard constituent containing the carbide or other abrasive precipitates from the solution.

As a specific example of one manner of practicing process, I will describe the production of high-speed steel by dissolving tungsten car- 93.8%' tungsten and about 6.2% carbon.

hide inabath of tungsten high-speed steel and casting the solution to reprecipitate a tungstencontaining carbide. It will be understood that other ferrous alloy baths may be used and that instead of employing tungsten carbide, I may use any of the other carbides or other abrasives which have been referred to previously.

A molten bath of a modified high-speed steel is prepared according to any good steel making process in a crucible, electric, or other furnace. The composition of this bath is such that after the carbide additions hereinafter described have.

been made, the ultimate composition will approximate the following analysis:

Example 1 Percent Carbon .75 Silicon .25 Manganese .25 Sulphur I .025 Phosphorus .035 Tungst n 18.00 Chromium 4.00 Vanadium 1, 25

Balance iron with the usual impurities.

It is preferred to use furnace conditions which are non-oxidizing or only slightly oxidizing in order to prevent undue loss of tungsten carbide by oxidation.

While the bath is maintained in a molten condition, tungsten carbide, preferably in finely divided form, is added to the bath, the amount of tungsten carbide varying according to the properties which it is desired,that the alloy shall have. For many purposes, about 10% by weight of tungsten carbide is added to the bath, the tungsten carbide containing approxima ztlslly e addition .of the tungsten carbide is preferably -made just previous to teeming and the bath .of

metal preferably is protected by a suitable slag to further guard against oxidation. After themay consist of complex carbides of iron and tungsten, or carbides of tungsten and other alloying elements which arepresent in the specific almy to, which tungsten carbide has been added.

These carbides which are reprecipitated from solution when the bath is cooled differ from the ordinary carbides which'are produced according to the usual steel-making processes in which the tungsten or other alloying element is added either inelem'ental form or in the form of a fenalloy and separately from the carbon with which it ultimately unites to form a'carbide. Where tungsten carbide, for example, is dissolved in an alloy steel bath and thereafter caused to reprecipitate, the hard carbides so precipitated 'generally present sharper cutting edges and are usually more angular than the tungsten bearing carbide which is formed in the ordinary manner by separately adding tungsten and carbon to a steel bath in accordance with usual steel-making processes and at a time long enough before casting to cause thorough dissemination of the dissolved tungsten and carbon throughout the bath. These unusual carbides formed according to my method may be clearly distinguished under the microscope from the usual carbides formed according to the present general practice. The usual carbides are more rounded or globular in shape and do not present such sharp angular cutting edges.

Reprecipitation of the carbides depends not only upon the quantity of carbide which is added to the bath, but also upon the time at which the addition is made. I may use a less quantity of the carbide than can be dissolved, a quantity which is approximately that which the bath can. ,dissolve, or an excess quantity so that the bath is incapable of dissolving all of the carbide which is added at normal bath temperatures. For any given quantity of carbide which is added to the bath, the amount which is dissolved will depend, among other factors, upon the temperature of the bath and the time at which the addition is made; that is, if the tungsten carbide is added shortly before teeming,,there will be less of the carbide dissolved than if the addition is made a longer time before teeming. It is preferred to add the carbide just before teeming, so that, although a portion of the carbide dissolves in the bath, there will be an undissolved portion which acts asa nucleus for the reprecipitation of the carbide when the alloy is cast. Where small amounts of the carbide are used and it is desired to have a portion of the carbide in the undissolved condition, the addition should be made immediately prior to casting. However. when larger quantities are used, the addition may be made a longer time before casting and there will still be a portion of the carbide in its undissolved condition. If agreater amount of the carbide is used than can be dissolved in the bath, the addition can be made a relatively long time before teeming, since a portion of the carbide will remain undissolved and will act as a nucleus for the reprecipitation of hard carbides when. the alloy is cast.

Under certain conditions, it is advisable to make the carbide additions in the ladle or in the ingot molds, or during intermediate pouring operations.

'Reprecipitation of carbides from solution is aided not only by a nucleus of undissolved carbide, but also, although to a lesser extent, by locally enriched carbide areas in the bath. .If the addition is made shortly before teeming, in accordance with my process, even though all of the carbide may be dissolved, its dissolved components will not be thoroughly disseminated throughout the bath, and there will be local areas which are richer in carbide components than the rest of the bath. These locally enriched areas will aid in the reprecipitation of thecarbidesical analysis:-

enriched carbide areas" as used in the claims, I mean not only those areas which contain some particles of undissolved carbide, but also those areas in which the carbide is entirely dissolved, but which contain a greater proportion of the dissolved components of the carbide than other portions of the bath.

In carrying out the present invention, the quantity of carbide or other abrasive, and the time of addition preferably are such as to form locally enriched areas which act as nuclei for the reprecipitation of hard carbides or other hard abrasives when the bath metal is cast. As has been stated-above, this method of causing reprecipitation of the hard carbides results in the production of unusual carbides which differ from those produced according to the usual steel-making operations in that the unusual carbides of my process are more angular and present sharper cutting edges and appear to be of a different composition than the usual carbides.

As an illustration, I have described my method wherein tungsten carbide is added'to a highspeed steel containing tungsten, chromium, and vanadium. It is to be understood that the invention is. not limited to the use of tungsten carbide, but that other carbides or abrasives may be employed, and that these materials may be dissolved in other ferrous alloy baths. The compositions of these baths are such that after the carbide additions, or additions of. other abrasives, have been made, the ultimate composition will approximate the following analyses and the alloys which are produced may be classed as follows. These analyses and classifications of 11;: the alloys are merely illustrative and are not given by way of limiting the invention thereto. The kind and amount of carbide or other abrasive which is used depends upon the ultimate composition desired.

Example 2 A cobalt high-speed steel of the type which may be represented by the following analysis:

. 8.50 Balance iron with usual impurities.

" Example 3 Manganese steel of the type which may be represented by the following typical analysis:

- Per cent Carbon .80 Silicon .25 14L Manganese 13.00 Sulphur .030 Phosphorus .040 Tungsten 10.00. Balance iron with usual impurities.

Example 4 A high-carbon, high-chrome, steel of the type which may be represented by the following typmanganese, contains chromium and tungsten, of

Balance iron with usual impurities.

the type which may be represented by the fol lowing typical analysis:

Per cent Carbon .85 Silic n .25 Manganese- 1.50

Sulphur .030 Phosphorus .030 Chromium .50 Tun sten .50

Balance iron with usual impurities.

' Example 7 So-called stainless steels and irons of the types which may be represented by the following typical analyses:

Type A Per cen Carbon .85 Silicon .20 Manganese .30 Chromium 13.50 Sulphur. .030 Phosphorus .030 Balance iron with usual impurities.

' Type B I Per cent Car .85 Si icon .25 Manganese .35 V Chr 17.00" Sulphur .030 Phosphorus v .030

Balance iron with usual impurities.

Type C Per cent Carbon-" .18 Sim .30 Manganese .40 Chromium 18.0 Sulphur .030 Phosp .030 Nickel 8.00

incense 3 yer cent Type D Carbom 2.25 Per cent Silicon .30 Carbon .09 Manganese 0 silicon .30 Sulphur D30 Manganese .40 0 Phosphorus .030 Chromium 12.00 Chromium 12.50 Sulphur .030 Balance iron with usual imp uitles 7 Phosphorus .030

Nickel .45 Y Example 5 Balance iron with usual impurities. as A high-carbon, high-chrome steel with molyb- E l 8 denum and vanadium present of the type which camp 8 may b r p s nt d y t following typ al a aly- A chrome-vanadium steel of the type which sis: may be represented by the following typical Per cent m Per cent ggfff: :22 Carbon .40 Silicon .25 Man a es B5 manganese .25 Sulphur .030

Chromium 3.50 05 Phosphorus .030 Chrnmium 12.50 Vanadium Loo Balance iron with usual impurities. Molybdenum 1.00

Example 9 An alloy having a composition between that 1% of cast iron and a true steel:

Balance iron with usual impurities.

A portion of the exceptional cutting properties of high-speed steels is attributable to the presence of tungsten bearing carbides. In such alloys, tungsten bearing carbides are formed only to a M5 limited extent, the formation of this desirable of carbon and tungsten which could be added as such in the production of high-speed steel alloys. It would ordinarily be presumed that whether tungsten and carbon, as such, are added 180 :to high-speed tool steels, or whether tungsten carbide is added, the amounts of tungsten and carbon which could be added without seriously affecting the ability of the alloy to be hot shaped, would be the same. However, this is not the case, for I have discovered that a'much higher percentage of tungsten and carbon can be added to steel and the steel will still be capable of being hot shaped, if they are added in the form oi tungsten carbide than is possible if they are added as elements. This condition, which would not be foreseen by one skilled in the art, enables me to produce high-speed steel which, because of the greater amounts or diflerent character of tungsten bearing carbides which it contains, has properties which make it greatly superior to ordinary high-speed steel; without the disadvantages which have previously been mentioned.

In Example 1. 10% oftungsten carbide was dissolved in analloy steel bath. This percentage the type alloy which it is desired to produce and the particular alloy bath to which the tungsten carbide is added. Some alloys will dissolve a greater percentage of tungsten carbide, or other of the carbides mentioned, or other abrasives, than will be dissolved by other alloys. It ordinarily is desirable to add as large a percentage of abrasive to the alloy as can be dissolved or the ultimate desired composition will permit and which will still enable the alloyv to be hot-shaped or worked in accordance with usual practice. In cases where the alloy is cast in substantially finished shape and, for this reason, does not require hot working, an amount of abrasive even beyond the point of saturation may be added to the alloy.

Other hard carbides, such as hereinbefore mentioned, or other abrasives may be dissolved and thereafter reprecipitated from solution in a manner substantially similar to that described in connection with the use of tungsten carbide.

When any of the chromium carbides Cr4C, Cr'zCs,

CrsCz are added to an alloy steel bath andreprecipitated from solution, an alloy steel having great resistance to abrasion is produced. The chromium carbide is preferably added just previous to teeming the steel, so that there will be either particles of undissolved chromium carbide or areas which are locally enriched in the carbide components which act as nuclei for the reprecipitation of hard chromium-containing carbides. using an induction furnace which sets up agitation of the bath as a result ofv its electric construction, thereby eliminating the necessity of stirring the carbide into the bath mechanically.

In the production of many alloys, one part of molybdenum is considered the equivalent of two point, but up to the present time, it has not beenfound practical to use more than about 5 or 6% of molybdenum, since when this amount is exceeded, the structure of the steel is bad and this leads to a high percentage rejection of the steel in the process of workingv or forging it to shape.

Furthermore, when more than about'5 or 6% of molybdenum is used, there is a high loss of molybdenum during forging. For this reason, the sub;- stitution of molybdenum for tungsten in highspeed steels has notv been satisfactory up to the present time. Molybdenum may, however, be

substituted for tungsten if the molybdenum is used in the form of molybdenum carbide and is dissolved in the steel bath and thereafter precipitated fromsolution. The carbides formed according to the present invention differ from those produced in the usual steel-making processes, as has been described previously Not all of the tungsten need be replaced by molybdenum, it being preferable to retain a small amount, say, 3 or 4% of tungsten, and to substitute molybdenum for the remainder of the tungsten. This results in a material decrease in the cost of the alloy steel.

, It has been proposed heretofore to add tantalum to high-speed steel with the idea of improving the red hardness properties of such alloys and also with the idea of increasing their capacity for cutting metals, since it was believed Good results have been obtained by that the. addition of tantalum would increase the formation of tantalum bearing carbides. The addition oftantalum, however, has not proved entirely satisfactory, for the reason, it is believed, that suflicient quantities of tantalum bearing carbides have not been formed. The amount of tantalum in carbide form may be increased, however, if the tantalum is added in the form of tantalum carbide to a steel bath and then caused to reprecipitate from solution in accordance with the present invention. The-other carbides hereinbefore mentioned may be used in asimilar manner to increase the cutting properties or resistance to abrasion of various ferrous alloys.

The amount of any of the carbides which is added to the bath depends not only upon the particular carbide which is used, the particular alloy bath to which the carbide is added, but also on the type of alloy which it is desired to produce.

-Where it is desired to produce an alloy which can be hot shaped, it is advisable not to use more than 50% of the carbide, and generally not more than 30%. An addition of even of carbide has a noticeablebeneficial affect in some cases.

although the amount generally used is between 5 and 20%.

Instead of using hard carbides, thesilicides ofthe corresponding metals may be employed in a generally similar manner, but with inferior re- .sults. The reprecipitation of silicides in place of carbides requires a .high silicon content in the By the term "alloy steel as used in the claims I mean steel containing one or more alloying components such as tungsten, chromium, manganese, molybdenum, vanadium and' cobalt in amounts at least as great as 1%. I

I have described in detail the method which is employed in carrying out my invention when tungsten carbide is dissolved in a bath of highspeed steel and then reprecipitated from solution. It is to be understood that the inventionis not limited to this particular carbide or to a bath of high-speed steel, but that other hard abrasives or mixtures of abrasives may be employed in place of the tungsten carbide and other ferrous alloys may be employed in place of the high-speed steel. Furthermore, the amounts of abrasive material may be varied according to the particular circumstances, and the invention may beotherwise practiced within the scope of the following claims.

I claim:

1. The process of making ferrous alloys, comprising dissolving a carbide of a metal of the thorium, uranium and columbiumin a ferrous alloy bath maintained under substantially nonoxidizing conditions, the addition being made shortly before teeming and without opportunity for thorough dissemination of the carbide, thereby resulting in areas locally enriched in carbide components which. act asnuclei for the reprecipitation of hard carbides on cooling, and casting to reprecipitate a hard carbide.

2. The process of making ferrous alloys, comprising dissolving a carbide of a metal of the group consisting of tungsten, chromium, molybdenum, vanadium, titanium, tantalum, zirconium, thorium, uranium and columbium in a ferrous alloy bath maintained under substantially nonoxidizing conditions, the quantity of carbide and the time of addition being such that a portion of the carbide remains undissolved so as to act as nuclei for the reprecipitation of hard carbides, and casting to reprecipitate a hard carbide.

3. The process of making ferrous alloys, comprising dissolving a carbide of a metal of the group consisting of tungsten, chromium, molybdenum, vanadium, titanium, tantalum, zirconium, thorium, uranium and columbium in a ferrous alloy bath maintained under substantially non-oxidizing conditions, the quantity of carbide and the time of addition being such as to form locally enriched carbide areas which act as nuclei for the reprecipitation of hard carbides when the bath is cooled, and casting to repre-' cipitate a hard carbide.

4. The process of making ferrous alloys, comprising dissolving a carbide of a metal of the group consisting of tungsten, chromium, molybdenum, vanadium, titanium, taltalum, zirconium, thorium, uranium and columbium in a ferrous alloy bath maintained under substantially non-oxidizing conditions, the addition of carbide being made shortly before teeming so as to produce locally enriched carbide areas which act as nuclei for the reprecipitation of hard carbides when the bath is cooled, and casting to reprecipitate a hard carbide.

5. The process of making ferrous alloys, comprising dissolving in a ferrous alloy bath maintained under substantially non-oxidizing conditions a carbide of a metal of the tungsten group, the amount of carbide added being such that when the bath is cooled a hard carbide will precipitate, and casting to reprecipitate the hard carbide.

6. The process of making ferrous alloys, comprising dissolving in a ferrous alloy bath maintained under substantially non-oxidizing conditions a carbide of a metal of the tungsten group,

' the quantity of carbide and the time of addition being such as to form locally enriched carbide areas which act as nuclei for reprecipitation of hard carbides when the bath is cooled, and casting to reprecipitate a hard carbide.

7. The process of making ferrous alloys, comprising dissolving tungsten carbide in a ferrous alloy bath maintained under substantially nonoxidizing conditions, the quantity of carbide and the time of addition being such as to form locally enriched carbide areas which act as nuclei for the repreoipitation of tungsten-containing carbides when the bath is cooled, and casting to reprecipi- ,tate a tungsten-containing carbide.

- group consisting of tungsten, chromium, molybdenum, vanadium, titanium, tantalum, zirconium, thorium, uranium and columbium in a bath of high-speed steel maintained under substantially non-oxidizing conditions, the amount of carbide added being such that when the bath is cooled a hard-carbide will precipitate, and casting to reprecipitate a hard carbide.

10. The process of making ferrous alloys, comprising disolving a carbide of a metal of the group consisting of tungsten, chromium, molyb denum, vanadium, titanium, tantalum, zirconium,

thorium, uranium and columbium in a bath of high-speed steel maintained under substantially non-oxidizingconditions, the quantity of carbide and the time of addition being such as to produce locally enriched carbide areas which act as nuclei for the reprecipitation-of hard carbides when the bath is cooled, and casting to reprecipitate a hard carbide.

11. The process of making ferrous alloys, comprising dissolving in a bath of highspeed steel maintained under substantially non-oxidizing conditions a carbide of a metal of the tungsten group, the quantity of carbide and the time of addition being such as to form locally enriched carbide areas which act as nuclei for the reprecipitation of hard carbides when'the bath is cooled, and casting to reprecipitate a carbide of a metal of the tungsten group.

12. The process of making ierrousalloys, which comprises providing high-speed steel in molten condition, dissolvingin the molten steel maintained under substantially non-oxidizing conditions tungsten and carbon in the form of tungsten 'carbide in quantity sufiicient to produce an alloy having more than 20% tungsten'and more than 1% carbon, and casting the alloy.

13. The process of making ferrous alloys suitable for the production of tools or other articles having great resistance to abrasion such as cutting tools, forming tools,'dies and the like, which comprises dissolving tungsten carbide in an alloy steel bath maintained under substantially nonoxidizing conditions, and casting the solution to form an ingot and precipitate a carbide of tungsten from the alloy.

14. The process of making ferrous alloys suitable for the production of tools or other articles having great resistance, to abrasion such as cutting tools, forming tools, dies and the like, which comprises dissolving tungsten carbide in a bath 1 g of high-speed steel in a crucible furnace while maintaining the bath under substantially nonoxidizing conditions; and casting the solution to form an ingot and precipitate a carbide of tungsten from the alloy. 13m

15. The process of making ferrous alloys suitable for the production of tools. or other articles having greatresistance to abrasion, such as cutting tools, forming tools, dies and the like, which comprises dissolving from 5 to 20% of tungsten 5 carbide in a ferrous alloy bath maintainedunder substantially non-oxidizing conditions, and casting the solution to precipitate a carbide of tungsten from the solution.

16. The process of making ferrous alloys sult- 3g able for the production of tools or other articles having great resistance to abrasion, such as cutting tools, forming tools, dies and the like, which comprises dissolving about 10% of tungsten carbide in a ferrous alloy bath maintained under 5 substantially non-oxidizing conditions, and casting the solution to precipitate a carbide of tungsten from the solution.

1'7. The process of making ferrous alloys suitable for the production of tools or other articles having great resistance to abrasion, such cutting tools, forming tools, dies and the like, which comprises adding to an alloy steel bath maintained under substantially non-oxidizing conditions tungsten carbide in amount greater: than can be dissolved by the alloy, and casting the mixture.

18. The process of making ferrous alloys suitable for the production of tools or other articles having great resistance to abrasion, such as cut- 50 ting tools, forming tools, dies and the like, which comprises adding to a ferrous alloy bath maintained undersubstantially non-oxidizing conditions from 5 to 49% of tungsten carbide, thereby dissolving at least a part of the tungsten carbide,

and casting to precipitate a carbide of tungsten.

19. The process of 'making ferrous alloys, comprising dissolving tantalum carbide in a ferrous alloy bath maintained under substantially nonoxidizing conditions and casting the solution to precipitate a hard tantalum containing carbide.

20. The process of making ferrous alloys suitable for the. production of tools or other articles having-great resistance to abrasion such as cutting tools, forming tools, dies and the like, which comprises dissolving a carbide of a metal of the tungsten group in an alloy steel bath maintained under substantially non-oxidizing conditions, and casting the solution to form an ingot and precipitate a carbide of the metal of the tungsten group from the alloy.

21. The process or making ferrous alloys, comprising adainga ten-o alloy to a ma bath to produce an alloy steel bath, adding to the alloy steel bath maintained under substantially nonoxidizing conditions a carbide o'i' a metal of the group consisting of tungsten, chromium, molybdenum, vanadium, titanium, tantalum, zirconium, thorium, uranium and columbium, and casting to reprecipitate a hard carbide.

22. The process oi'making ferrous alloys, comprising adding a term alloy-to a steel bath to produce an alloy steel bath, adding to the alloy steel bath maintained under substantially nonoxidizing conditions a carbide of the metal of 

